Replace nose with pytest

[MeggyCal]

On Python 3.9 or 3.10 nose will stop working, so let us transform the tests to pytest.

Sorry, I do not know how to purge nose from Pipfile.lock, could you please do it yourself?

[MeggyCal]

Now I made it to run at least on ubuntu and macos. How do I set the PYTHONPATH on Windows, please?

[cscorley]

Hello,

Thank you so much for this change!

Instead of PYTHONPATH=, I think the preferred method is to run pytest directly in GitHub actions, according to this document: https://docs.github.com/en/actions/language-and-framework-guides/using-python-with-github-actions#testing-your-code

For my personal dev, I use pipenv: https://pipenv.pypa.io/en/latest/. I would ordinarily uninstall nose with pipenv uninstall nose, and then install pytest with pipenv install pytest --dev. I can fix pipenv after your changes :) It is not required by the build or publish.

[cscorley]

This should be able to run without PYTHONPATH=

pytest --doctest-modules --doctest-glob='*.rst'

This works locally for me on Windows

[MeggyCal]

I am quite certain I tried it (only with py.test, not pytest) and that it failed on Ubuntu

[cscorley]

I see. Yes, you're right. It is still failing.

The only difference I see at this point between this branch and the documentation is that the documentation installs pytest in the same stage that it executes under. That could be the last possible difference, but I'm not sure why it would matter at all (I'd guess nose and pytest install differently).

I am happy to merge this change and then work on getting the build action working again separately. The changes themselves to the tests are good :)